inner classes

inner class:

We can have two types of inner classes:  static inner classes and non-static inner classes

non-static inner classes requires initialization of outer class.

Whereas, static inner class doesn’t require initialization of outer class.

Note: We can not declare an outer class static. We can only use static keyword with inner classes.

Benefit of static inner classes:

static inner class doesn’t contain a reference of outer class. So, on screen rotation [In Mobile device, like Android], it doesn’t create m/m leak. While non-static inner class contains reference of outer class and can cause m/m leak.

Lets learn how to instantiate static and non-static inner classes:

Instantiation of static class:

public class OuterClass{

     public OuterClass(){

     }

    static class InnerClass{
     
          public void check(){

          }

    }

}


public class OuterInnerDemo{

       public static void main(String[] args){
     
               OuterClass.InnerClass nestedObject = new  OuterClass.InnerClass();
               nestedObject.check();

       }

}


Instantiation of non-static class:

public class OuterClass{

     public OuterClass(){

  

     }

    class InnerClass{

       

          public void check(){

          }

    }

}

public class OuterInnerDemo{

       public static void main(String[] args){

        

               OuterClass outer = new OuterClass();

               OuterClass.InnerClass nonStaticObject =  outer.new  InnerClass();

               nonStaticObject.check();

       }

}

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Thanks